Several advancements in brass instrument construction took place beginning at the end of the 19th century, when conical instruments such as the cornet and euphonium began replacing the more cylindrical instruments of the trumpet family. The newer instruments were often constructed with leadpipes that enhanced the instrument's tone and dynamic capabilities by extending the already tapered or elliptical backbore of the mouthpiece. The leadpipes were configured either as straight tapered leadpipes or as elliptically tapered leadpipes.
The shape of the leadpipe influence the quality of the sound produced when playing the instrument. Leadpipes with a straight taper produce a sound that can be described as more compact but more intense than the sound from an elliptical leadpipe. In contrast, leadpipes with elliptical configurations have more resonance, creating a fuller sound.
Over time, the elliptical leadpipe has become the preferred leadpipe configuration used in trombones, and is used on most other brass instruments as well. A drawback of the elliptical leadpipe is that it is less efficient than the straight taper leadpipe, thereby requiring more effort to play than a leadpipe with a straight taper.
Although many brass instruments have permanently fixed leadpipes, interchangeable leadpipes may be used on trombones, especially professional trombones, to give the player more sound-producing options. Interchangeable leadpipes in trombones may be soldered to a threaded collar affixed within a threaded receiver at the entrance of the first inner slide tube of the trombone.
The combination of a leadpipe and the backbore of a brass instrument functions as a waveguide after the sound passes through the mouthpiece, directing the energy of the sound wave from the leadpipe into the bore of the instrument. Existing leadpipes generally have one of two different configurations. The first is an elliptically tapered configuration downstream of the venturi. The second configuration is one in which the leadpipe has a straight taper downstream of the venturi.
Several improvements directed at improving the sound quality of brass instruments have been disclosed. Both U.S. Pat. No. 3,474,698 and U.S. Pat. No. 5,847,300 disclose devices that improve the sound of the instrument by minimizing the gap created when inserting a mouthpiece into the leadpipe of a brass instrument.
U.S. Pat. No. 6,087,572 discloses an adjustable receiver that allows players to adjust the relative position of the mouthpiece and leadpipe, thereby allowing some flexibility in the style of music produced.
U.S. Pat. No. 4,273,020 (the '020 patent) discloses a method to improve the sound of a brass instrument by creating a zone of increasing taper between the mouthpiece and valve section of the instrument, thereby improving the acoustic qualities of the instrument. The '020 patent discloses a leadpipe with a plurality of sections. The side of each section generally defines a frustum. Moving from the mouthpiece end of the leadpipe, the sides of each respective section increase in taper, resulting in a chromatic scale that is true to the desired pitch.